This invention relates to top activated eyelets, or rivets, which may be utilized to secure electrical connectors to printed circuit boards and, more particularly, to an improved eyelet and an improved tool for gripping and activating the eyelet.
U.S. Pat. No. 4,717,219 discloses an eyelet for assembling an electrical connector to a printed circuit board. The electrical connector is formed with a mounting flange having an aperture therethrough. The aperture through the flange is adapted to be in registration with a corresponding aperture through the printed circuit board, with an eyelet of the disclosed design extending through both apertures. The eyelet has a flange engaging the mounting flange of the electrical connector, an inverted conical end remote from the flange and a generally tubular shank extending therebetween. The inverted conical end of the eyelet is splayed, or expanded, into contact with the lower surface of the printed circuit board by activation through the bore of the tubular shank to secure the electrical connector to the printed circuit board.
The eyelet disclosed in the '219 patent is preferably utilized in conjunction with a robotic tool which splays the inverted conical end of the eyelet. It is typically a requirement that when splaying the inverted conical end, no forces be applied to the robot arm, the electrical connector or the printed circuit board. All such forces are to be contained within the eyelet. U.S. Pat. No. 4,750,261 discloses a robotic tool for gripping and activating the eyelet so that this requirement is met. The disclosed tool includes a plunger insertable into the tubular shank of the eyelet for engagement with the inverted conical end to splay the inverted conical end. A split collet surrounds the plunger and is formed with grip heads at its end. The collet extends into the tubular shank of the eyelet and, when the plunger is extended to engage the inverted conical end of the eyelet, the collet is expanded so that the grip heads, which have exterior barbs, engage against and tightly grip the internal surface of the eyelet within its tubular shank.
In the arrangement disclosed in the '219 patent, the aperture through the mounting flange of the electrical connector is formed with spaced longitudinal protrusions, or ribs. Therefore, the tubular shank of the eyelet is free to expand within the aperture between the protrusions and only a relatively low force is required to be exerted by the grip heads to grip the eyelet The '219 patent also discloses a grounding strap which extends on the undersurface of the electrical connector mounting flange around the aperture. An additional function of the eyelet is to provide an electrical ground connection between the electrical connector and the printed circuit board. The eyelet is therefore formed of a conductive metal. It has been found that in order to ensure a good electrical connection from the grounding strap to the eyelet, an additional open eyelet is preferably inserted into the mounting flange aperture from the bottom. This additional eyelet has a lower flange which engages the grounding strap, and when the eyelet of the '219 patent is inserted with a press fit into the mounting flange aperture through the additional eyelet, a secure electrical connection between the '219 eyelet and the grounding strap is effected. However, when using the additional eyelet, this eliminates the room for expansion of the tubular shank of the '219 eyelet between the longitudinal protrusions of the aperture. This increases the force required to grip the inside of the tubular shank of the eyelet.
It is therefore an object of the present invention to provide an improved eyelet of the type described, and a tool for use therewith, wherein only a relatively small force is required to grip the eyelet.